The present invention relates generally to an internal combustion engine being designed to reduce the harmful emissions in the auto exhaust gas therefrom, and more specifically to an internal combustion engine having an improved mechanism for mixing air with the fuel being supplied thereto for the purpose of reducing such harmful emissions of the exhaust gas.
As one mode of burning fuel in internal combustion engines developed for the purpose of reducing the harmful auto emissions, various engines have been proposed under the designation of torch-ignition engines or stratified combustion engines.
In the typical torch-ignition engine, however, an auxiliary combustion chamber is provided separately from the main combustion chamber in the cylinder head and the auxiliary combustion chamber is equipped with its own suction hole or inlet and its own suction valve. A rich mixture taken in through this suction hole of the auxiliary combustion chamber when the suction valve thereof opens is introduced into the auxiliary combustion chamber, and this rich mixture is ignited by the spark plug. Using the torch of ignition, the mixture in the main combustion chamber, which is too lean to be ignited by an ordinary spark, is ignited, thereby reducing the harmful emissions due to the burning of the lean mixture. In this method, however, although the harmful emissions may reliably be reduced, it is unavoidable that the structure of the cylinder head becomes extremely complicated and accordingly expensive, primarily because the auxiliary combustion chamber required thereby has to be equipped with its own suction valve.
By contrast, in the typical stratified combustion engine, just short of the suction valve within the suction port opening in the combustion chamber, which is equivalent to the main combustion chamber, set up within the cylinder, a rich mixture must be introduced through an inlet path separately provided from the main suction path. This rich mixture layer is kept around the spark plug within the combustion chamber, while the lean mixture layer is kept outside and away from the rich mixture, and thereby the same effect being aimed at in the torch-ignition engine described hereinbefore, is attained. In the stratified combustion engine, the auxiliary combustion chamber is unnecessary and the cylinder head can be simplified, but on the other hand, it is extremely difficult to keep the rich mixture stratum within one area of the combustion chamber in the cylinder and the lean mixture in another area. Thus, it is difficult to practicably apply this engine as an automobile internal combustion engine which has to be operated over a wide range from low to high speeds and to secure the effect of reducing the harmful emissions in the exhaust gas being emitted therefrom.